Tam Valley Booster And Circuit Breaker

Now and then on Facebook I see a post from someone on DCC who manages to run a loco into a live-frog turnout that's been set against the loco's direction of travel. Most of the time, this will cause a short that will trigger the booster's or the command station's circuit breaker -- but not always. If the circuit breaker doesn't trip, this will heat up the loco's wheels very quickly, and something will melt within seconds. It's happened to me several times, and as I've posted here, I've had to send to Walthers to get replacement trucks for the affected locos.

This, by the way, is te sort of thing that the extravagantly priced model railroad magazines don't cover. I gave my hobby budget a real boost when I droppped my subscriptions. You get Facebook with your internet connection, and I think it's a good deal.

Recently I saw a comment replying to one of those Facebook posts, saying that the best solution to the problem of DCC booster circuit breakers not tripping is to put a Tam Valley DAB002 booster between the DCC booster or command station and the layout. I've already been using Tam Valley Frog Juicers, which operate by having a circuit breaker that trips faster than a regular DCC circuit breaker, and when it detects a short at the frog, it quickly shifts the polarity before the DCC circuit breaker can trip.

The Tam Valley DAB002 is priced reasonably enough -- certainly lower than an NCE SB5 -- so I decided to give it a try. The Tam Valley documentation is sketchy, divided between a leaflet with the product and an entry on their website. It took me a certain amount of trial and error to get it correctly installed. Below is a photo of it on my HO layout:

The DAB002 is the green PC board mounted on the L girder on the upper right. It is meant to sit between the outrput of the NCE SB5 at lower left and the layout's DCC bus. There are 3 main ports, all on the right side of the board. The top port is the DCC OUT port on the right side of the DAB002. This takes the DCC output from the SB5 booster to the layout DCC bus. Unfortunately, it has two screw terminals similar to the ones on the SB5, when best practice for a DCC bus is 16 AWG wire, so you need to splice in short pieces of 22 AWG (yellow in the photo) to connect the 16 AWG DCC bus to the screw terminals on the DAB002.

The second port from the top is DCC IN. It takes the DCC input from the TRACK output of the SB5 via the blue and white wires in the photo coming from the TRACK output on the SB5.

The third port from the top is Power Input. This must come from a common 5 AMP AC-DC adapter that puts out 12-16 volts DC via a coaxial plug, typical of DCC power supplies. This isn't supplied with the booster. Tam Valley sells them, but you can find them more cheaply on eBay in the $8-10 range. The documentation doesm't make it clear that you need this for the unit to work.

When everything has been installed correctly, there are three red LEDs, one under each port, that should light up as shown in the photo. If the circuit breaker trips, the LED under the top, DCC OUT, port will dim to about hslf brightness. This is the only short-circuit indication you will get, and it will trip before the DCC booster or command station breaker trips. This means you won't get any flash or beep from the booster or command station for a short, as they won't know anything is wromg, since the Tam Valley breaker will have beaten them to it.

The documentation doesn't make it clear that the board with the LEDs must be visible during layout operation so you can tell if there's a short been detected.

I'm hoping that the DAB002 prevents any further melted gears on my locos. It has already tripped for one short before the SB5 breaker could trip.